This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Development work on large-scale detector arrays for XAS measurements reached the performance goals defined in the grant application for the current program period, and a purchase requisition was placed after approval by the SMB Advisory Committee. The detector is for XAS measurements of ultra-dilute biological samples on SSRL?s beam line 9-3. It is based on 100 ea of 5 mm x 5 mm Ge detector elements fabricated as monolithic elements on one substrate crystal. They are therefore spatially arranged without any dead space in between, enhancing the collection area of the fluorescence signal. Having many smaller elements enhances the count-rate capability. With an energy resolution representative of array detectors consisting of individual elements, the performance of this new detector is expected to be outstanding. The monolithic arrangement furthermore enables the detector to be positioned as close as possible to the sample, as it will have a narrow front end. This detector therefore provides the highest collection efficiency in area coverage, within the smallest possible area, meeting both detector performance and geometric requirements. Delivery (from Canberra, Inc.) is expected in early 2009, as is the associated digital signal processing electronics.